This research project plans to examine the amounts of the major soybean isoflavones in soy foods and determine their bioavailability in humans. This will be accomplished by measuring the amounts of genistin, daidzin, their aglycones, genistein and daidzein, the 6"-0-acetyl forms of the glucosides in an array of soy foods. The effects of processing and storage on the distribution of the isoflavones will be examined by manufacturing soy foods from specific varieties of soybeans. The bioavailability of the soy isoflavones will be assessed by administering single doses of isoflavones in various soy foods to human subjects. The plasma, urine and fecal distribution of the isoflavones and their metabolites will be determined. These data will provide a base for understanding the absorption and metabolism of soybean isoflavones in humans and an accurate data base on the levels of these compounds in typical soy foods. These data will contribute to an overall understanding of the potential impact of soybeans on cancer prevention and lead to further research on the mechanisms of action for soybean isoflavones in cancer prevention.